Ricta Slix White Skateboard Wheels - 52mm 81b (Set of 4) Ricta Slix: Grind Faster - Grind Longer! The revolution in skateboard wheel technology continues... Ricta Slix combine our NRG Formula, proven THE fastest urethane in skateboarding, with a custom molded TPU slide insert for three times more slip and minimal drag on the inside of the wheel for longer and faster grinds. 81b is hard and fast!